diff mbox

[v2,2/2] drm: bridge/dw_hdmi: add dw hdmi i2c bus adapter support

Message ID 1431952341-20823-3-git-send-email-vladimir_zapolskiy@mentor.com (mailing list archive)
State New, archived
Headers show

Commit Message

Vladimir Zapolskiy May 18, 2015, 12:32 p.m. UTC
The change adds support of internal HDMI I2C master controller, this
subdevice is used by default, if "ddc-i2c-bus" DT property is omitted.

The main purpose of this functionality is to support reading EDID from
an HDMI monitor on boards, which don't have an I2C bus connected to
DDC pins.

Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
---
Changes since v1:
- fixed a devm_kfree() signature
- split completions for read and write operations

 drivers/gpu/drm/bridge/dw_hdmi.c | 341 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 335 insertions(+), 6 deletions(-)

Comments

Philipp Zabel May 19, 2015, 10:43 a.m. UTC | #1
Hi Vladimir,

Am Montag, den 18.05.2015, 15:32 +0300 schrieb Vladimir Zapolskiy:
> The change adds support of internal HDMI I2C master controller, this
> subdevice is used by default, if "ddc-i2c-bus" DT property is omitted.
> 
> The main purpose of this functionality is to support reading EDID from
> an HDMI monitor on boards, which don't have an I2C bus connected to
> DDC pins.
> 
> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>

Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
on imx6q-nitrogen6x with the DDC pads muxed to HDMI_TX.

regards
Philipp
Russell King - ARM Linux Aug. 13, 2015, 10:56 p.m. UTC | #2
On Mon, May 18, 2015 at 03:32:21PM +0300, Vladimir Zapolskiy wrote:
> +/* HDMI_IH_I2CM_STAT0 and HDMI_IH_MUTE_I2CM_STAT0 register bits */
> +#define HDMI_IH_I2CM_STAT0_ERROR		BIT(0)
> +#define HDMI_IH_I2CM_STAT0_DONE			BIT(1)
> +
> +/* HDMI_I2CM_OPERATION register bits */
> +#define HDMI_I2CM_OPERATION_READ		BIT(0)
> +#define HDMI_I2CM_OPERATION_READ_EXT		BIT(1)
> +#define HDMI_I2CM_OPERATION_WRITE		BIT(4)
> +
> +/* HDMI_I2CM_INT register bits */
> +#define HDMI_I2CM_INT_DONE_MASK			BIT(2)
> +#define HDMI_I2CM_INT_DONE_POL			BIT(3)
> +
> +/* HDMI_I2CM_CTLINT register bits */
> +#define HDMI_I2CM_CTLINT_ARB_MASK		BIT(2)
> +#define HDMI_I2CM_CTLINT_ARB_POL		BIT(3)
> +#define HDMI_I2CM_CTLINT_NAC_MASK		BIT(6)
> +#define HDMI_I2CM_CTLINT_NAC_POL		BIT(7)

Please put these definitions in dw_hdmi.h

> +
> +
>  #define HDMI_EDID_LEN		512
>  
>  #define RGB			0
> @@ -102,6 +124,19 @@ struct hdmi_data_info {
>  	struct hdmi_vmode video_mode;
>  };
>  
> +struct dw_hdmi_i2c {
> +	struct i2c_adapter	adap;
> +
> +	spinlock_t		lock;
> +	struct completion	cmp_r;
> +	struct completion	cmp_w;
> +	u8			stat;
> +
> +	u8			operation_reg;
> +	u8			slave_reg;
> +	bool			is_regaddr;
> +};
> +
>  struct dw_hdmi {
>  	struct drm_connector connector;
>  	struct drm_encoder *encoder;
> @@ -111,6 +146,7 @@ struct dw_hdmi {
>  	struct device *dev;
>  	struct clk *isfr_clk;
>  	struct clk *iahb_clk;
> +	struct dw_hdmi_i2c *i2c;
>  
>  	struct hdmi_data_info hdmi_data;
>  	const struct dw_hdmi_plat_data *plat_data;
> @@ -179,6 +215,249 @@ static void hdmi_mask_writeb(struct dw_hdmi *hdmi, u8 data, unsigned int reg,
>  	hdmi_modb(hdmi, data << shift, mask, reg);
>  }
>  
> +static void dw_hdmi_i2c_init(struct dw_hdmi *hdmi)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&hdmi->i2c->lock, flags);
> +
> +	/* Set Fast Mode speed */
> +	hdmi_writeb(hdmi, 0x0b, HDMI_I2CM_DIV);
> +
> +	/* Software reset */
> +	hdmi_writeb(hdmi, 0x00, HDMI_I2CM_SOFTRSTZ);
> +
> +	/* Set done, not acknowledged and arbitration interrupt polarities */
> +	hdmi_writeb(hdmi, HDMI_I2CM_INT_DONE_POL, HDMI_I2CM_INT);
> +	hdmi_writeb(hdmi, HDMI_I2CM_CTLINT_NAC_POL | HDMI_I2CM_CTLINT_ARB_POL,
> +		    HDMI_I2CM_CTLINT);
> +
> +	/* Clear DONE and ERROR interrupts */
> +	hdmi_writeb(hdmi, HDMI_IH_I2CM_STAT0_ERROR | HDMI_IH_I2CM_STAT0_DONE,
> +		    HDMI_IH_I2CM_STAT0);
> +
> +	/* Mute DONE and ERROR interrupts */
> +	hdmi_writeb(hdmi, HDMI_IH_I2CM_STAT0_ERROR | HDMI_IH_I2CM_STAT0_DONE,
> +		    HDMI_IH_MUTE_I2CM_STAT0);
> +
> +	spin_unlock_irqrestore(&hdmi->i2c->lock, flags);

What exactly is this spinlock protecting against with the above code?

> +}
> +
> +static int dw_hdmi_i2c_read(struct dw_hdmi *hdmi,
> +			    unsigned char *buf, int length)
> +{
> +	int stat;
> +	unsigned long flags;
> +	struct dw_hdmi_i2c *i2c = hdmi->i2c;
> +
> +	spin_lock_irqsave(&i2c->lock, flags);
> +
> +	i2c->operation_reg = HDMI_I2CM_OPERATION_READ;
> +
> +	if (!i2c->is_regaddr) {
> +		dev_dbg(hdmi->dev, "set read register address to 0\n");
> +		i2c->slave_reg = 0x00;
> +		i2c->is_regaddr = true;
> +	}
> +
> +	while (length--) {
> +		reinit_completion(&i2c->cmp_r);

If you're re-initialising the completion on every byte, why do you need
separate completions for the read path and the write path?

If a single completion can be used, you then don't have to store the
operation register value in struct dw_hdmi_i2c either.

> +		i2c->stat = 0;

What use does zeroing this have?  You don't read it, except after you've
had a successful completion, which implies that the interrupt handler must
have written to it.

> +
> +		hdmi_writeb(hdmi, i2c->slave_reg++, HDMI_I2CM_ADDRESS);
> +		hdmi_writeb(hdmi, i2c->operation_reg, HDMI_I2CM_OPERATION);
> +
> +		spin_unlock_irqrestore(&i2c->lock, flags);
> +
> +		stat = wait_for_completion_interruptible_timeout(&i2c->cmp_r,
> +								 HZ / 10);
> +		if (!stat)
> +			return -ETIMEDOUT;
> +		if (stat < 0)
> +			return stat;

Can a DDC read/write really be interrupted and restarted correctly?
Won't this restart the transaction from the very beginning?  Have
you validated that all code paths calling into here can cope with
-ERESTARTSYS?

If you look at drm_do_probe_ddc_edid() for example, it will retry
the transfer if you return -ERESTARTSYS here, but as the signal has
not been handled, wait_for_completion_interruptible_timeout() will
immediately return -ERESTARTSYS again... and again... and again.
Each time will queue another operation _without_ waiting for the
last one to complete.

> +
> +		spin_lock_irqsave(&i2c->lock, flags);
> +
> +		/* Check for error condition on the bus */
> +		if (i2c->stat & HDMI_IH_I2CM_STAT0_ERROR) {
> +			spin_unlock_irqrestore(&i2c->lock, flags);
> +			return -EIO;
> +		}
> +
> +		*buf++ = hdmi_readb(hdmi, HDMI_I2CM_DATAI);
> +	}
> +
> +	spin_unlock_irqrestore(&i2c->lock, flags);

I'd be very surprised if you need the spinlocks in the above code.
You'll see the update to i2c->stat after the completion, becuase
wait_for_completion*() is in the same class as the other event-waiting
functions, and contains barriers which will ensure that you will not
read i2c->stat before you see the completion even on SMP platforms.

> +
> +	return 0;
> +}
...
> +static int dw_hdmi_i2c_xfer(struct i2c_adapter *adap,
> +			    struct i2c_msg *msgs, int num)
> +{
> +	struct dw_hdmi *hdmi = i2c_get_adapdata(adap);
> +	struct dw_hdmi_i2c *i2c = hdmi->i2c;
> +
> +	int i, ret;
> +	u8 addr;
> +	unsigned long flags;
> +
> +	dev_dbg(hdmi->dev, "xfer: num: %d, addr: 0x%x\n", num, msgs[0].addr);
> +
> +	spin_lock_irqsave(&i2c->lock, flags);
> +
> +	hdmi_writeb(hdmi, 0x00, HDMI_IH_MUTE_I2CM_STAT0);
> +
> +	/* Set slave device address from the first transaction */
> +	addr = msgs[0].addr;
> +	hdmi_writeb(hdmi, addr, HDMI_I2CM_SLAVE);
> +
> +	/* Set slave device register address on transfer */
> +	i2c->is_regaddr = false;
> +
> +	spin_unlock_irqrestore(&i2c->lock, flags);
> +
> +	for (i = 0; i < num; i++) {
> +		dev_dbg(hdmi->dev, "xfer: num: %d/%d, len: %d, flags: 0x%x\n",
> +			i + 1, num, msgs[i].len, msgs[i].flags);
> +
> +		if (msgs[i].addr != addr) {
> +			dev_warn(hdmi->dev,
> +				 "unsupported transaction, changed slave address\n");
> +			ret = -EOPNOTSUPP;
> +			break;
> +		}

Probably ought to validate that before starting any transaction?

> +
> +		if (msgs[i].len == 0) {
> +			dev_dbg(hdmi->dev,
> +				 "unsupported transaction %d/%d, no data\n",
> +				 i + 1, num);
> +			ret = -EOPNOTSUPP;
> +			break;
> +		}

Ditto.

> +
> +		if (msgs[i].flags & I2C_M_RD)
> +			ret = dw_hdmi_i2c_read(hdmi, msgs[i].buf, msgs[i].len);
> +		else
> +			ret = dw_hdmi_i2c_write(hdmi, msgs[i].buf, msgs[i].len);
> +
> +		if (ret < 0)
> +			break;
> +	}
> +
> +	if (!ret)
> +		ret = num;
> +
> +	spin_lock_irqsave(&i2c->lock, flags);
> +
> +	/* Mute DONE and ERROR interrupts */
> +	hdmi_writeb(hdmi, HDMI_IH_I2CM_STAT0_ERROR | HDMI_IH_I2CM_STAT0_DONE,
> +		    HDMI_IH_MUTE_I2CM_STAT0);
> +
> +	spin_unlock_irqrestore(&i2c->lock, flags);

What exactly is this spinlock protecting us from?  A single write to a
register is always atomic.

> +
> +	return ret;
> +}
> +
> +static u32 dw_hdmi_i2c_func(struct i2c_adapter *adapter)
> +{
> +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static struct i2c_algorithm dw_hdmi_algorithm = {

const?

> +	.master_xfer	= dw_hdmi_i2c_xfer,
> +	.functionality	= dw_hdmi_i2c_func,
> +};
> +
> +static struct i2c_adapter *dw_hdmi_i2c_adapter(struct dw_hdmi *hdmi)
> +{
> +	struct i2c_adapter *adap;
> +	int ret;
> +
> +	hdmi->i2c = devm_kzalloc(hdmi->dev, sizeof(*hdmi->i2c), GFP_KERNEL);
> +	if (!hdmi->i2c)
> +		return ERR_PTR(-ENOMEM);

I'd much prefer:
	struct dw_hdmi_i2c *i2c;

	i2c = devm_kzalloc(...);

> +
> +	spin_lock_init(&hdmi->i2c->lock);
> +	init_completion(&hdmi->i2c->cmp_r);
> +	init_completion(&hdmi->i2c->cmp_w);
> +
> +	adap = &hdmi->i2c->adap;
> +	adap->class = I2C_CLASS_DDC;
> +	adap->owner = THIS_MODULE;
> +	adap->dev.parent = hdmi->dev;
> +	adap->algo = &dw_hdmi_algorithm;
> +	strlcpy(adap->name, "DesignWare HDMI", sizeof(adap->name));
> +	i2c_set_adapdata(adap, hdmi);
> +
> +	ret = i2c_add_adapter(adap);
> +	if (ret) {
> +		dev_warn(hdmi->dev, "cannot add %s I2C adapter\n", adap->name);
> +		devm_kfree(hdmi->dev, hdmi->i2c);
> +		hdmi->i2c = NULL;
> +		return ERR_PTR(ret);
> +	}
> +

	hdmi->i2c = i2c;

rather than having to remember to clear out hdmi->i2c in error paths.

> +	dev_info(hdmi->dev, "registered %s I2C bus driver\n", adap->name);
> +
> +	return adap;
> +}
> +
>  static void hdmi_set_cts_n(struct dw_hdmi *hdmi, unsigned int cts,
>  			   unsigned int n)
>  {
> @@ -1466,16 +1745,47 @@ struct drm_bridge_funcs dw_hdmi_bridge_funcs = {
>  	.mode_fixup = dw_hdmi_bridge_mode_fixup,
>  };
>  
> +static irqreturn_t dw_hdmi_i2c_irq(struct dw_hdmi *hdmi)
> +{
> +	struct dw_hdmi_i2c *i2c = hdmi->i2c;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&i2c->lock, flags);
> +
> +	i2c->stat = hdmi_readb(hdmi, HDMI_IH_I2CM_STAT0);
> +	if (!i2c->stat) {
> +		spin_unlock_irqrestore(&i2c->lock, flags);
> +		return IRQ_NONE;
> +	}
> +
> +	hdmi_writeb(hdmi, i2c->stat, HDMI_IH_I2CM_STAT0);
> +
> +	if (i2c->operation_reg & HDMI_I2CM_OPERATION_READ)
> +		complete(&i2c->cmp_r);
> +	else
> +		complete(&i2c->cmp_w);
> +
> +	spin_unlock_irqrestore(&i2c->lock, flags);

Again, what function does this spinlock perform?  Wouldn't:

	unsigned int stat;

	stat = hdmi_readb(hdmi, HDMI_IH_I2CM_STAT0);
	if (stat == 0)
		return IRQ_NONE;

	/* Clear interrupts */
	hdmi_writeb(hdmi, stat, HDMI_IH_I2CM_STAT0);

	i2c->stat = stat;

	if (i2c->operation_reg & HDMI_I2CM_OPERATION_READ)
		complete(&i2c->cmp_r);
	else
		complete(&i2c->cmp_w);

be fine, or maybe with the spinlock around the assignment to i2c->stat
and this point if you need the assignment and completion to be atomic?

Note that the write to 'i2c->stat' would be atomic in itself anyway.

In any case, complete() implies a write memory barrier, so even on SMP
systems, the write to i2c->stat will be visible before the completion
"completes".  So, I don't think you need any locking here.

Thanks.
diff mbox

Patch

diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index 49cafb6..7f64e73 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -1,15 +1,17 @@ 
 /*
+ * DesignWare High-Definition Multimedia Interface (HDMI) driver
+ *
+ * Copyright (C) 2013-2015 Mentor Graphics Inc.
  * Copyright (C) 2011-2013 Freescale Semiconductor, Inc.
+ * Copyright (C) 2010, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
- * Designware High-Definition Multimedia Interface (HDMI) driver
- *
- * Copyright (C) 2010, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
  */
+
 #include <linux/module.h>
 #include <linux/irq.h>
 #include <linux/delay.h>
@@ -28,6 +30,26 @@ 
 
 #include "dw_hdmi.h"
 
+/* HDMI_IH_I2CM_STAT0 and HDMI_IH_MUTE_I2CM_STAT0 register bits */
+#define HDMI_IH_I2CM_STAT0_ERROR		BIT(0)
+#define HDMI_IH_I2CM_STAT0_DONE			BIT(1)
+
+/* HDMI_I2CM_OPERATION register bits */
+#define HDMI_I2CM_OPERATION_READ		BIT(0)
+#define HDMI_I2CM_OPERATION_READ_EXT		BIT(1)
+#define HDMI_I2CM_OPERATION_WRITE		BIT(4)
+
+/* HDMI_I2CM_INT register bits */
+#define HDMI_I2CM_INT_DONE_MASK			BIT(2)
+#define HDMI_I2CM_INT_DONE_POL			BIT(3)
+
+/* HDMI_I2CM_CTLINT register bits */
+#define HDMI_I2CM_CTLINT_ARB_MASK		BIT(2)
+#define HDMI_I2CM_CTLINT_ARB_POL		BIT(3)
+#define HDMI_I2CM_CTLINT_NAC_MASK		BIT(6)
+#define HDMI_I2CM_CTLINT_NAC_POL		BIT(7)
+
+
 #define HDMI_EDID_LEN		512
 
 #define RGB			0
@@ -102,6 +124,19 @@  struct hdmi_data_info {
 	struct hdmi_vmode video_mode;
 };
 
+struct dw_hdmi_i2c {
+	struct i2c_adapter	adap;
+
+	spinlock_t		lock;
+	struct completion	cmp_r;
+	struct completion	cmp_w;
+	u8			stat;
+
+	u8			operation_reg;
+	u8			slave_reg;
+	bool			is_regaddr;
+};
+
 struct dw_hdmi {
 	struct drm_connector connector;
 	struct drm_encoder *encoder;
@@ -111,6 +146,7 @@  struct dw_hdmi {
 	struct device *dev;
 	struct clk *isfr_clk;
 	struct clk *iahb_clk;
+	struct dw_hdmi_i2c *i2c;
 
 	struct hdmi_data_info hdmi_data;
 	const struct dw_hdmi_plat_data *plat_data;
@@ -179,6 +215,249 @@  static void hdmi_mask_writeb(struct dw_hdmi *hdmi, u8 data, unsigned int reg,
 	hdmi_modb(hdmi, data << shift, mask, reg);
 }
 
+static void dw_hdmi_i2c_init(struct dw_hdmi *hdmi)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&hdmi->i2c->lock, flags);
+
+	/* Set Fast Mode speed */
+	hdmi_writeb(hdmi, 0x0b, HDMI_I2CM_DIV);
+
+	/* Software reset */
+	hdmi_writeb(hdmi, 0x00, HDMI_I2CM_SOFTRSTZ);
+
+	/* Set done, not acknowledged and arbitration interrupt polarities */
+	hdmi_writeb(hdmi, HDMI_I2CM_INT_DONE_POL, HDMI_I2CM_INT);
+	hdmi_writeb(hdmi, HDMI_I2CM_CTLINT_NAC_POL | HDMI_I2CM_CTLINT_ARB_POL,
+		    HDMI_I2CM_CTLINT);
+
+	/* Clear DONE and ERROR interrupts */
+	hdmi_writeb(hdmi, HDMI_IH_I2CM_STAT0_ERROR | HDMI_IH_I2CM_STAT0_DONE,
+		    HDMI_IH_I2CM_STAT0);
+
+	/* Mute DONE and ERROR interrupts */
+	hdmi_writeb(hdmi, HDMI_IH_I2CM_STAT0_ERROR | HDMI_IH_I2CM_STAT0_DONE,
+		    HDMI_IH_MUTE_I2CM_STAT0);
+
+	spin_unlock_irqrestore(&hdmi->i2c->lock, flags);
+}
+
+static int dw_hdmi_i2c_read(struct dw_hdmi *hdmi,
+			    unsigned char *buf, int length)
+{
+	int stat;
+	unsigned long flags;
+	struct dw_hdmi_i2c *i2c = hdmi->i2c;
+
+	spin_lock_irqsave(&i2c->lock, flags);
+
+	i2c->operation_reg = HDMI_I2CM_OPERATION_READ;
+
+	if (!i2c->is_regaddr) {
+		dev_dbg(hdmi->dev, "set read register address to 0\n");
+		i2c->slave_reg = 0x00;
+		i2c->is_regaddr = true;
+	}
+
+	while (length--) {
+		reinit_completion(&i2c->cmp_r);
+		i2c->stat = 0;
+
+		hdmi_writeb(hdmi, i2c->slave_reg++, HDMI_I2CM_ADDRESS);
+		hdmi_writeb(hdmi, i2c->operation_reg, HDMI_I2CM_OPERATION);
+
+		spin_unlock_irqrestore(&i2c->lock, flags);
+
+		stat = wait_for_completion_interruptible_timeout(&i2c->cmp_r,
+								 HZ / 10);
+		if (!stat)
+			return -ETIMEDOUT;
+		if (stat < 0)
+			return stat;
+
+		spin_lock_irqsave(&i2c->lock, flags);
+
+		/* Check for error condition on the bus */
+		if (i2c->stat & HDMI_IH_I2CM_STAT0_ERROR) {
+			spin_unlock_irqrestore(&i2c->lock, flags);
+			return -EIO;
+		}
+
+		*buf++ = hdmi_readb(hdmi, HDMI_I2CM_DATAI);
+	}
+
+	spin_unlock_irqrestore(&i2c->lock, flags);
+
+	return 0;
+}
+
+static int dw_hdmi_i2c_write(struct dw_hdmi *hdmi,
+				  unsigned char *buf, int length)
+{
+	int stat;
+	unsigned long flags;
+	struct dw_hdmi_i2c *i2c = hdmi->i2c;
+
+	spin_lock_irqsave(&i2c->lock, flags);
+
+	i2c->operation_reg = HDMI_I2CM_OPERATION_WRITE;
+
+	if (!i2c->is_regaddr) {
+		if (length) {
+			/* Use the first write byte as register address */
+			i2c->slave_reg = buf[0];
+			length--;
+			buf++;
+		} else {
+			dev_dbg(hdmi->dev, "set write register address to 0\n");
+			i2c->slave_reg = 0x00;
+		}
+		i2c->is_regaddr = true;
+	}
+
+	while (length--) {
+		reinit_completion(&i2c->cmp_w);
+		i2c->stat = 0;
+
+		hdmi_writeb(hdmi, *buf++, HDMI_I2CM_DATAO);
+		hdmi_writeb(hdmi, i2c->slave_reg++, HDMI_I2CM_ADDRESS);
+		hdmi_writeb(hdmi, i2c->operation_reg, HDMI_I2CM_OPERATION);
+
+		spin_unlock_irqrestore(&i2c->lock, flags);
+
+		stat = wait_for_completion_interruptible_timeout(&i2c->cmp_w,
+								 HZ / 10);
+		if (!stat)
+			return -ETIMEDOUT;
+		if (stat < 0)
+			return stat;
+
+		spin_lock_irqsave(&i2c->lock, flags);
+
+		/* Check for error condition on the bus */
+		if (i2c->stat & HDMI_IH_I2CM_STAT0_ERROR) {
+			spin_unlock_irqrestore(&i2c->lock, flags);
+			return -EIO;
+		}
+	}
+
+	spin_unlock_irqrestore(&i2c->lock, flags);
+
+	return 0;
+}
+
+static int dw_hdmi_i2c_xfer(struct i2c_adapter *adap,
+			    struct i2c_msg *msgs, int num)
+{
+	struct dw_hdmi *hdmi = i2c_get_adapdata(adap);
+	struct dw_hdmi_i2c *i2c = hdmi->i2c;
+
+	int i, ret;
+	u8 addr;
+	unsigned long flags;
+
+	dev_dbg(hdmi->dev, "xfer: num: %d, addr: 0x%x\n", num, msgs[0].addr);
+
+	spin_lock_irqsave(&i2c->lock, flags);
+
+	hdmi_writeb(hdmi, 0x00, HDMI_IH_MUTE_I2CM_STAT0);
+
+	/* Set slave device address from the first transaction */
+	addr = msgs[0].addr;
+	hdmi_writeb(hdmi, addr, HDMI_I2CM_SLAVE);
+
+	/* Set slave device register address on transfer */
+	i2c->is_regaddr = false;
+
+	spin_unlock_irqrestore(&i2c->lock, flags);
+
+	for (i = 0; i < num; i++) {
+		dev_dbg(hdmi->dev, "xfer: num: %d/%d, len: %d, flags: 0x%x\n",
+			i + 1, num, msgs[i].len, msgs[i].flags);
+
+		if (msgs[i].addr != addr) {
+			dev_warn(hdmi->dev,
+				 "unsupported transaction, changed slave address\n");
+			ret = -EOPNOTSUPP;
+			break;
+		}
+
+		if (msgs[i].len == 0) {
+			dev_dbg(hdmi->dev,
+				 "unsupported transaction %d/%d, no data\n",
+				 i + 1, num);
+			ret = -EOPNOTSUPP;
+			break;
+		}
+
+		if (msgs[i].flags & I2C_M_RD)
+			ret = dw_hdmi_i2c_read(hdmi, msgs[i].buf, msgs[i].len);
+		else
+			ret = dw_hdmi_i2c_write(hdmi, msgs[i].buf, msgs[i].len);
+
+		if (ret < 0)
+			break;
+	}
+
+	if (!ret)
+		ret = num;
+
+	spin_lock_irqsave(&i2c->lock, flags);
+
+	/* Mute DONE and ERROR interrupts */
+	hdmi_writeb(hdmi, HDMI_IH_I2CM_STAT0_ERROR | HDMI_IH_I2CM_STAT0_DONE,
+		    HDMI_IH_MUTE_I2CM_STAT0);
+
+	spin_unlock_irqrestore(&i2c->lock, flags);
+
+	return ret;
+}
+
+static u32 dw_hdmi_i2c_func(struct i2c_adapter *adapter)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm dw_hdmi_algorithm = {
+	.master_xfer	= dw_hdmi_i2c_xfer,
+	.functionality	= dw_hdmi_i2c_func,
+};
+
+static struct i2c_adapter *dw_hdmi_i2c_adapter(struct dw_hdmi *hdmi)
+{
+	struct i2c_adapter *adap;
+	int ret;
+
+	hdmi->i2c = devm_kzalloc(hdmi->dev, sizeof(*hdmi->i2c), GFP_KERNEL);
+	if (!hdmi->i2c)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock_init(&hdmi->i2c->lock);
+	init_completion(&hdmi->i2c->cmp_r);
+	init_completion(&hdmi->i2c->cmp_w);
+
+	adap = &hdmi->i2c->adap;
+	adap->class = I2C_CLASS_DDC;
+	adap->owner = THIS_MODULE;
+	adap->dev.parent = hdmi->dev;
+	adap->algo = &dw_hdmi_algorithm;
+	strlcpy(adap->name, "DesignWare HDMI", sizeof(adap->name));
+	i2c_set_adapdata(adap, hdmi);
+
+	ret = i2c_add_adapter(adap);
+	if (ret) {
+		dev_warn(hdmi->dev, "cannot add %s I2C adapter\n", adap->name);
+		devm_kfree(hdmi->dev, hdmi->i2c);
+		hdmi->i2c = NULL;
+		return ERR_PTR(ret);
+	}
+
+	dev_info(hdmi->dev, "registered %s I2C bus driver\n", adap->name);
+
+	return adap;
+}
+
 static void hdmi_set_cts_n(struct dw_hdmi *hdmi, unsigned int cts,
 			   unsigned int n)
 {
@@ -1466,16 +1745,47 @@  struct drm_bridge_funcs dw_hdmi_bridge_funcs = {
 	.mode_fixup = dw_hdmi_bridge_mode_fixup,
 };
 
+static irqreturn_t dw_hdmi_i2c_irq(struct dw_hdmi *hdmi)
+{
+	struct dw_hdmi_i2c *i2c = hdmi->i2c;
+	unsigned long flags;
+
+	spin_lock_irqsave(&i2c->lock, flags);
+
+	i2c->stat = hdmi_readb(hdmi, HDMI_IH_I2CM_STAT0);
+	if (!i2c->stat) {
+		spin_unlock_irqrestore(&i2c->lock, flags);
+		return IRQ_NONE;
+	}
+
+	hdmi_writeb(hdmi, i2c->stat, HDMI_IH_I2CM_STAT0);
+
+	if (i2c->operation_reg & HDMI_I2CM_OPERATION_READ)
+		complete(&i2c->cmp_r);
+	else
+		complete(&i2c->cmp_w);
+
+	spin_unlock_irqrestore(&i2c->lock, flags);
+
+	return IRQ_HANDLED;
+}
+
 static irqreturn_t dw_hdmi_hardirq(int irq, void *dev_id)
 {
 	struct dw_hdmi *hdmi = dev_id;
 	u8 intr_stat;
+	irqreturn_t ret = IRQ_NONE;
+
+	if (hdmi->i2c)
+		ret = dw_hdmi_i2c_irq(hdmi);
 
 	intr_stat = hdmi_readb(hdmi, HDMI_IH_PHY_STAT0);
-	if (intr_stat)
+	if (intr_stat) {
 		hdmi_writeb(hdmi, ~0, HDMI_IH_MUTE_PHY_STAT0);
+		return IRQ_WAKE_THREAD;
+	}
 
-	return intr_stat ? IRQ_WAKE_THREAD : IRQ_NONE;
+	return ret;
 }
 
 static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
@@ -1654,6 +1964,13 @@  int dw_hdmi_bind(struct device *dev, struct device *master,
 	 */
 	hdmi_init_clk_regenerator(hdmi);
 
+	/* If DDC bus is not specified, try to register HDMI I2C bus */
+	if (!hdmi->ddc) {
+		hdmi->ddc = dw_hdmi_i2c_adapter(hdmi);
+		if (IS_ERR(hdmi->ddc))
+			hdmi->ddc = NULL;
+	}
+
 	/*
 	 * Configure registers related to HDMI interrupt
 	 * generation before registering IRQ.
@@ -1674,11 +1991,18 @@  int dw_hdmi_bind(struct device *dev, struct device *master,
 	/* Unmute interrupts */
 	hdmi_writeb(hdmi, ~HDMI_IH_PHY_STAT0_HPD, HDMI_IH_MUTE_PHY_STAT0);
 
+	/* Unmute I2CM interrupts and reset HDMI DDC I2C master controller */
+	if (hdmi->i2c)
+		dw_hdmi_i2c_init(hdmi);
+
 	dev_set_drvdata(dev, hdmi);
 
 	return 0;
 
 err_iahb:
+	if (hdmi->i2c)
+		i2c_del_adapter(&hdmi->i2c->adap);
+
 	clk_disable_unprepare(hdmi->iahb_clk);
 err_isfr:
 	clk_disable_unprepare(hdmi->isfr_clk);
@@ -1699,13 +2023,18 @@  void dw_hdmi_unbind(struct device *dev, struct device *master, void *data)
 
 	clk_disable_unprepare(hdmi->iahb_clk);
 	clk_disable_unprepare(hdmi->isfr_clk);
-	i2c_put_adapter(hdmi->ddc);
+
+	if (hdmi->i2c)
+		i2c_del_adapter(&hdmi->i2c->adap);
+	else
+		i2c_put_adapter(hdmi->ddc);
 }
 EXPORT_SYMBOL_GPL(dw_hdmi_unbind);
 
 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
 MODULE_AUTHOR("Andy Yan <andy.yan@rock-chips.com>");
 MODULE_AUTHOR("Yakir Yang <ykk@rock-chips.com>");
+MODULE_AUTHOR("Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>");
 MODULE_DESCRIPTION("DW HDMI transmitter driver");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:dw-hdmi");